Hust. (Hustedt, 1958: 174, figs 165, 166)
Cells solitary and tapered towards ends in apical view, distinctly constricted in the middle and with truncate ends in girdle view; apical axis 55–86 µm; transapical axis 5–7 µm. Transapical striae straight, 26–30 in 10 µm. Fibulae 8–12 in 10 µm.
Plough I. and coastal waters off Davis Station, East Antarctica; in stomach contents of Salpa fusiformis in the Antarctic, 69°43’S 06°30’E (Hustedt, 1958).
At first glance, N. medioconstricta can be confused with Auricula compacta , particularly in girdle view. However, the latter is usually a much longer cell (79–134 µm), and it has fewer fibulae (6–9 per 10 µm).